1. Field of the Invention
The present invention generally relates to a system and method for determining whether a secondary infusion has been properly set up and administered. More specifically, the present invention relates to a system including an infusion pump having a sensor that is capable of monitoring and detecting pressure within the container-side of a fluid infusion set. The pressure sensor is used to monitor the pressure within the container-side of the infusion set and provides signals that may be analyzed by a processor to determine, for example only, and not by way of limitation, whether a check-valve in a primary infusion line is working properly, whether the differential height of the primary and secondary fluid containers is correct, and whether a manual valve in the secondary infusion line has been opened and generally whether the secondary infusion line provides an unobstructed flow path to the secondary fluid container. The processor is programmed to provide a signal to care-givers in an institution, or store a record of the event in an institutional database, in response to determining that a fault in the infusion set up has been detected.
2. General Background and State of the Art
Infusion of therapeutic fluids to treat or nourish patients is commonly used in hospitals and other medical care institutions. Originally, such infusions were carried out by hanging a bag or container of therapeutic fluid from a pole so that fluid flows under the force of gravity regulated by a user-controllable restrictor through a length of tubing and into the lumen of a vessel of a patient. More recently, the flow of fluid into the patient is accomplished under the control of a programmed infusion pump located in the fluid pathway. Infusion pumps are useful in that they allow for more precise control of the low of therapeutic fluid into the patient. For example, using an infusion pump, relatively precise amounts of fluid may be infused at controlled rates. Moreover, the rate of infusion may be altered during the infusion by programming the pump to pump the fluid at a different rate. This capability is useful where a bolus of therapeutic fluid is desired to initiate an infusion regimen, with the rate then being decreased to a reduced flow rate for the remainder of the infusion.
Although standard infusion sets have typically provided for the administration of a single fluid, the need to administer two different fluids to a patient is not uncommon. Typically, such a need arises when a patient must have a maintenance solution delivered and, concomitantly with the administration of the maintenance fluid, there is a need for the intermittent infusion of a therapeutic solution. In such cases it has been the practice to use what is commonly referred to as a “piggyback” system wherein separate fluids from separate containers are sequentially infused through a common tube. Such systems have several obvious advantages. For instance, in a piggyback system the needle need not be removed from the patient whenever the administration of fluids changes from the maintenance solution to the therapeutic solution or vice versa. This fact, of course, causes less trauma to the patient, avoids unnecessary pain, and reduces the chances of infection. Furthermore, and equally important, the use of a piggyback system simplifies procedures for the nurse.
Several devices are employed in the sequential administration of two separate solutions to a patient. Basically, these systems comprise a primary administration set and a secondary administration set and rely on the varying differential of hydrostatic pressure at a check valve throughout the course of delivery for the sequencing of fluid flow within the system.
When the secondary container is set up, the primary container is typically placed below of the level of the secondary container, generally approximately eight inches below the primary container. The primary container may be left in this position, or it may be raised once the secondary container has emptied. Normally, a one-way check valve is included in the infusion line connecting the primary container to the infusion pump, and the infusion line from the secondary container is connected to the infusion line at a location below, or downstream, of the check valve. This check valve prevents therapeutic fluid from the secondary container from flowing upwards into the primary container, and may also be set to prevent flow of fluid from the primary container while fluid is flowing from the secondary container.
One problem occurs when the secondary container is incorrectly placed at or below the level of the primary container. When this happens, the differential hydrostatic pressure which would normally close the one-way check valve is non-existent. If the containers are so improperly placed, fluid from both the primary and secondary containers may flow into the pump concurrently, or if the secondary container is sufficiently lower than the primary container then primary fluid may flow into the secondary container. In either case, where the primary fluid and secondary fluid are incompatible, or if the infusion regimen calls for one the fluids to be sequentially infused in a necessary order, attention must be given to the infusion set up to correct the problem. Unfortunately, this problem may go un-noticed by a busy care-giver.
Typically, a manual valve (roller clamp, slide clamp etc.) is included in the secondary infusion line between the secondary container and the connection of the secondary infusion line to the infusion line that is connected to the pump. This valve is useful in that it allows for connection of the secondary fluid container to the infusion set up while infusion from the primary fluid is being infused, and is opened only when it is time to begin infusion from the secondary container. A problem occurs when the care-giver fails to open this valve, thus preventing the secondary infusion fluid from being pumped from the secondary container, in this situation the primary fluid will be infused at the secondary flow rate which may cause undesired medical consequences.
An additional problem occurs when the containers are in their proper position for automatic secondary infusion but the one-way check valve fails allowing fluid to flow bi-directionally. When this happens, fluid from the secondary container, because the secondary container is higher than the level of the primary container, and thus has a greater hydrostatic pressure than the fluid in the primary container may flow into the primary container, mixing with the primary fluid. This is disadvantageous for the reasons stated previously.
Still another potential problem in the administration and set up of a secondary infusion occurs when multiple fault conditions exist simultaneously. One such condition consists of a bidirectionally open one-way check valve fault and the manual valve on the secondary infusion line being inadvertently closed when it is intended to be open for secondary delivery.
Often, the secondary container is filled with a volume different from the volume that is programmed to be delivered. Typically, the pump is programmed with a “secondary” volume to be infused. Where the secondary container is overfilled, a volume of secondary fluid remains in the secondary container when the pump determines that the secondary volume to be infused parameter has been satisfied. When this happens, the pump, which may have been programmed to change its pumping rate when the secondary infusion is completed, begins pumping the remaining secondary fluid at the new rate, which may be too high a rate for the particular secondary fluid being infused.
Similarly, where the secondary container has been under-filled, the pump will exhaust the secondary container before the volume to be infused parameter is satisfied, and will continue pumping at the secondary infusion rate. However, due to the exhaustion of the fluid within the secondary container, the one-way check valve will open, and allow fluid from the primary container to flow into the infusion line. Thus, the pump may continue to pump primary infusion fluid at the secondary flow rate, this flow rate may be inappropriate for the primary fluid.
What has been needed and heretofore unavailable, is a simple and reliable system and method for detecting when an infusion container is empty, or nearly empty, and for providing a signal to an infusion pump to either alter the infusion rate, provide an alert signal to a care-giver that the container needs replenishment or replacement. Such a system should be able to detect when the height of the secondary infusion container is incorrect relative to the height of the primary infusion container, and should also be able to detect when the manual valve or clamp on the secondary infusion line has not been opened under the desired mode of operation. The system should also be capable of detecting a failure of the one-way valve, as well as certain multiple fault conditions. The present invention satisfies these and other needs.